General solution for slowly-rotating perfect fluid spheres in general relativity     

Mario C. Díaz  Jorge A. Pullin 《Astrophysics and Space Science》1988,148(2):385-388

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Anisotropic four loop superstring cosmologies     

Reinaldo J. Gleiser  Jorge Pullin 《Astrophysics and Space Science》1989,154(2):337-341

A spatially-homogenous and anisotropic cosmological model in self-creation theory of gravitation proposed by Barber is obtained when the source of gravitational field is a perfect fluid and the metric is of Marder's cyclindrically-symmetric form. Some properties of the model are discussed.  相似文献   

The inverse compton effect in the electrons of the Van Allen radiation belt     

Jorge Raul Albano 《Astrophysics and Space Science》1970,9(2):332-337

A first estimate of the energy that reaches the Earth's surface and is produced by the inverse Compton effect between the electrons in the Van Allen belt and the solar flux was made. Since in the belt there are electrons with energies between 0.5 and 7 MeV, it was possible to use the Klein-Nishina formula in an approximate form and estimate the energy that is Compton scattered by all the electrons in the Van Allen belt by using Vette, Lucero and Bright's model. The result was compared (a) with the measurements of the continuum in the regions of soft X-rays, and (b) with the energy that is produced by the trapped electrons through the synchrotron mechanism.This paper was presented at the COSPAR meeting held in leningrad on May 20–29, 1970.  相似文献   

An upgraded version of the Eta model   总被引：2，自引：0，他引：2  

Fedor Mesinger  Sin Chan Chou  Jorge L. Gomes  Dusan Jovic  Paulo Bastos  Josiane F. Bustamante  Lazar Lazic  André A. Lyra  Sandra Morelli  Ivan Ristic  Katarina Veljovic 《Meteorology and Atmospheric Physics》2012,116(3-4):63-79

Upgrades implemented over a number of years in an open source version of the Eta model, posted at the CPTEC web site http://etamodel.cptec.inpe.br/, are summarized and examples of benefits are shown. The version originates from the NCEP’s Workstation Eta code posted on the NCEP web site http://www.emc.ncep.noaa.gov/mmb/wrkstn_eta, which differs from the NCEP’s latest operational Eta by having the WRF-NMM nonhydrostatic option included. Most of the upgrades made resulted from attention paid to less than satisfactory performance noted in several Eta results, and identification of the reasons for the problem. Others came from simple expectation that including a feature that is physically justified but is missing in the code should help. The most notable of the upgrades are the introduction of the so-called sloping steps, or discretized shaved cells topography; piecewise-linear finite-volume vertical advection of dynamic variables; vapor and hydrometeor loading in the hydrostatic equation, and changes aimed at refining the convection schemes available in the Eta. Several other modifications have to do with the calculation of exchange coefficients, conservation in the vertical diffusion, and diagnostic calculation of 10-m winds. Several examples showing improved performance resulting from the dynamics changes are given. One includes a case of unrealistically low temperatures in several mountain basins generated by a centered vertical advection difference scheme’s unphysical advection from below ground, removed by its replacement with a finite-volume scheme. Another is that of increased katabatic winds in the Terra Nova Bay Antarctica region. Successful forecast of the severe downslope zonda wind case in the lee of the highest peaks of the Andes is also shown, and some of the recent successful verification results of the use of the upgraded model are pointed out. The code is used at numerous places, and along with setup information it is available for outside users at the CPTEC Eta web site given above.  相似文献   

Downscaling of South America present climate driven by 4-member HadCM3 runs   总被引：5，自引：2，他引：3  

Sin Chan Chou  José A. Marengo  André A. Lyra  Gustavo Sueiro  José F. Pesquero  Lincoln M. Alves  Gillian Kay  Richard Betts  Diego J. Chagas  Jorge L. Gomes  Josiane F. Bustamante  Priscila Tavares 《Climate Dynamics》2012,38(3-4):635-653

The objective of this work is to evaluate climate simulations over South America using the regional Eta Model driven by four members of an ensemble of the UK Met Office Hadley Centre HadCM3 global model. The Eta Model has been modified with the purpose of performing long-term decadal integrations and has shown to reproduce “present climate”—the period 1961–1990—reasonably well when forced by HadCM3. The global model lateral conditions with a resolution of 2.5° latitude?×?3.75° longitude were provided at a frequency of 6?h. Each member of the global model ensemble has a different climate sensitivity, and the four members were selected to span the range of uncertainty encompassed by the ensemble. The Eta Model nested in the HadCM3 global model was configured with 40-km horizontal resolution and 38 layers in the vertical. No large-scale internal nudging was applied. Results are shown for austral summer and winter at present climate defined as 1961–90. The upper and low-level circulation patterns produced by the Eta-CPTEC/HadCM3 experiment set-up show good agreement with reanalysis data and the mean precipitation and temperature with CRU observation data. The spread in the downscaled mean precipitation and temperature is small when compared against model errors. On the other hand, the benefits in using an ensemble is clear in the improved representation of the seasonal cycle by the ensemble mean over any one realization. El Ni?o and La Ni?a years were identified in the HadCM3 member runs based on the NOAA Climate Prediction Center criterion of sea surface temperature anomalies in the Ni?o 3.4 area. The frequency of the El Ni?o and La Ni?a events in the studied period is underestimated by HadCM3. The precipitation and temperature anomalies typical of these events are reproduced by most of the Eta-CPTEC/HadCM3 ensemble, although small displacements of the positions of the anomalies occur. This experiment configuration is the first step on the implementation of Eta-CPTEC/HadCM3 upcoming experiments on climate change studies that are discussed in a companion paper.  相似文献   

Spatial and temporal changes in dry-snow line altitude on the Antarctic Peninsula     

Jorge Arigony-Neto  Helmut Saurer  Jefferson C. Simões  Frank Rau  Ricardo Jaña  Steffen Vogt  Hermann Gossmann 《Climatic change》2009,94(1-2):19-33

Drastic changes were detected in glacial systems of the Antarctic Peninsula in the last decades. The observed phenomena comprise the disintegration of ice shelves, acceleration and thinning of glaciers, and retreat of glacier fronts. However, due to the lack of consistent systematic observations in particular of the higher parts of the glacial systems, it is difficult to predict further responses of the Antarctic Peninsula glaciers to climatic change. The present paper analyses spatial and temporal variations of changes in the dry-snow line altitude on the Antarctic Peninsula as extracted from a time series (1992–2005) of ERS-1/2 SAR and Envisat ASAR data. Upward changes in dry-snow line altitude were observed in general, and are attributed to extreme high-temperature events impacting the central plateaus of the Antarctic Peninsula and the increasing duration of warming periods. A mean decrease in dry-snow line altitude was detected on the west side of the peninsula and is identified as a response to recorded increase in precipitation and accumulation. These results validate the capability of SAR data for deriving superficial parameters of glaciers to be used as indicators of climatic changes in high-latitude regions where operational restrictions limit conventional meteorological observations.  相似文献   

Rebuttal to “Comment on “Evidence of electrical activity on Titan drawn from the Schumann resonances sent by Huygens probe” by J.A. Morente, J.A. Portí, A. Salinas, and E.A. Navarro [2008, Icarus, 195, 802-811]”     

Juan A. Morente  Jorge A. Portí  Enrique A. Navarro 《Icarus》2009,204(1):352-354

Hamelin et al. criticize some conclusions of our paper [Morente, J.A., Portí, J.A., Salinas, A., Navarro, E.A., 2008. Icarus 195, 802-811]. This rebuttal is our response to their criticism. In our view, their comments are contradictory and not based on scientific argument. Our paper presents a comprehensible methodology for extracting weak resonances from the late-time response of systems with high losses and our conclusions are derived from and supported by this methodology, which was first checked using an analytical function and later with the data from a numerical simulation of Titan’s atmosphere. Conversely, the Comment of Hamelin et al. does not contain any mathematical proof, either supporting their statements or invalidating our analysis procedure.  相似文献   

Tidal disruption of globular clusters in dwarf galaxies with triaxial dark matter haloes     

Jorge Peñarrubia  Matthew G. Walker  Gerard Gilmore 《Monthly notices of the Royal Astronomical Society》2009,399(3):1275-1292

We use N -body simulations to study the tidal evolution of globular clusters (GCs) in dwarf spheroidal (dSph) galaxies. Our models adopt a cosmologically motivated scenario in which the dSph is approximated by a static Navarro, Frenk & White halo with a triaxial shape. We apply our models to five GCs spanning three orders of magnitude in stellar density and two in mass, chosen to represent the properties exhibited by the five GCs of the Fornax dSph. We show that only the object representing Fornax's least dense GC (F1) can be fully disrupted by Fornax's internal tidal field – the four denser clusters survive even if their orbits decay to the centre of Fornax. For a large set of orbits and projection angles, we examine the spatial and velocity distribution of stellar debris deposited during the complete disruption of an F1-like GC. Our simulations show that such debris appears as shells, isolated clumps and elongated overdensities at low surface brightness (≥26 mag arcsec⁻²), reminiscent of substructure observed in several Milky Way dSphs. Such features arise from the triaxiality of the galaxy potential and do not dissolve in time. The kinematics of the debris depends strongly on the progenitor's orbit. Debris associated with box and resonant orbits does not display stream motions and may appear 'colder'/'hotter' than the dSph's field population if the viewing angle is perpendicular/parallel to the progenitor's orbital plane. In contrast, debris associated with loop orbits shows a rotational velocity that may be detectable out to a few kpc from the galaxy centre. Chemical tagging that can distinguish GC debris from field stars may reveal whether the merger of GCs contributed to the formation of multiple stellar components observed in dSphs.  相似文献   

A new insight on the decreasing sea level trend over the Ionian basin in the last decades     

Jorge Del Río Vera  Francisco Criado-Aldeanueva  Jesús García-Lafuente  F. Javier Soto-Navarro 《Global and Planetary Change》2009,68(3):232-235

Altimetry measurements over the Ionian region and tide gauge records along the southern Italian coasts have been combined to analyse the negative sea level trend over the Ionian basin in the last decades. The apparent decreasing trend should be better understood as an abrupt sea level drop in 1998 probably linked to changes in the surface circulation in the Ionian basin induced by the Eastern Mediterranean Transient, which changed from anticyclonic to cyclonic about March 1998. From then onwards, a rising rate of 7.9 ± 0.9 mm/year is observed over the basin.  相似文献   

Accessory mineral U–Th–Pb ages and <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar eruption chronology,and their bearing on rhyolitic magma evolution in the Pleistocene Coso volcanic field,California     

Justin I. Simon  Jorge A. Vazquez  Paul R. Renne  Axel K. Schmitt  Charles R. Bacon  Mary R. Reid 《Contributions to Mineralogy and Petrology》2009,158(4):421-446

We determined Ar/Ar eruption ages of eight extrusions from the Pleistocene Coso volcanic field, a long-lived series of small volume rhyolitic domes in eastern California. Combined with ion-microprobe dating of crystal ages of zircon and allanite from these lavas and from granophyre geothermal well cuttings, we were able to track the range of magma-production rates over the past 650 ka at Coso. In ≤230 ka rhyolites we find no evidence of protracted magma residence or recycled zircon (or allanite) from Pleistocene predecessors. A significant subset of zircon in the ~85 ka rhyolites yielded ages between ~100 and 200 Ma, requiring that generation of at least some rhyolites involves material from Mesozoic basement. Similar zircon xenocrysts are found in an ~200 ka granophyre. The new age constraints imply that magma evolution at Coso can occur rapidly as demonstrated by significant changes in rhyolite composition over short time intervals (≤10’s to 100’s ka). In conjunction with radioisotopic age constraints from other young silicic volcanic fields, dating of Coso rhyolites highlights the fact that at least some (and often the more voluminous) rhyolites are produced relatively rapidly, but that many small-volume rhyolites likely represent separation from long-lived mushy magma bodies.  相似文献